Advances in crosscutting technologies have brought about convergence of data and voice networks. In particular, new services have been proposed that merge telephony and internetworking. As a caveat these services entail a higher degree of complexity. In view of the customer's satisfaction service providers strive to hide the complexity from the user and to offer levels of transparency comparable to PSTN (public switched telephone network) services.
Usually, combining PSTN switching and internetworking comes at the price of proprietary solutions and hence leads to a lack of interoperability and scalability. The deployment of well-established hardware components and standardised software solutions would be desirable to improve on this situation. A category of services where these observations apply are services based on PSTN calls that are controlled or monitored via an Internet terminal device, such as PSTN phone conferences started and controlled via a PC or PSTN calls triggered by clicking on a Web page (click-to-dial). Many of these services require real-time processing of control information, such as PSTN signalling, ISDN service parameters or notification messages.